The 40mm 2.8 stm seems to be costing £220 in the uk, thats $300!
Anyone know why this is?
Partly due to much lower sales tax in the US.
UK VAT (ie Sales Tax) is 20%.
Also if Canon overseas sales are priced in USD they may require further cushion if GBP falls vs USD - significant falls could happen in the current financial climate.
Anyway price differential still looks excessive!
Try say New York shop to see whether they will sell you one without local sales tax (because its an export).
Airmail would cost very little for such a tiny lens. Then add import duty and customs charges on the UK side - then VAT on everything so far. Could save a bit! Only worth it if lens has an international warranty.